If it was dramatically sharper than the Canon, I'd be interested, even if the Canon was cheaper. I have been afraid that Canon will never make another 24-105, opting instead lately for expensive lenses that stop or start at the 70mm cutoff (24-70 and 70-200 or 300).

The 24-105 focal range is just so much more versatile than the 24-70 it's not even funny. 70 mm is too short for what most people would say is good portrait length, and 70mm is generally also too short for sports, etc. That extra part from 71-105 adds a ton of usefulness for many things. If Sigma or Canon would release an improved 24-105 I would definitely be interested.

Wow. Maybe time to invest in some stocks. XDThe canon 24-105 L is going to be hard to beat at the current market.. But I'm impressed regardless. More competition, better for consumers. I have not seen one for 500! That's crazy!

Have to agree with Neuro.The current prices of the Canon and its real excellence will be a hard act to follow.

My copy needs a CLA buts is still a go-to lens for 80% of my shooting. What I really need is another for backup.

It is a decent lens, but not really an "excellent" one. It could use way more sharpness across the frame, especially in the corners. I wouldn't use the 24-105L for landscapes.

Sharpness is probably one of the things that Sigma is going to bring to the table.. And lots of it.

In my experience the 24-105 is plenty sharp. I rented the 24-70 2.8 L II and found it only a touch sharper than my lens. For real world work I have found it to be a great step up from the old 28-75 Tamron that was touted as the top "value" lens at the time ~4-5yrs ago.The real world for me is working with the vagaries of hand held shooting, motion and the use to which the final image is destined. Even the most demanding applications (large prints) are well served by this lens.

Studio shooting with side by side comparison to my Canon 100 macro (on camera stand) show the macro to have the edge in absolute sharpness and better contrast but no client will ever see the difference.

when the pro built Canon 24-105 f4 IS and 24-70 f4 IS already exist? And two f2.8 non IS variants also exist. one that set the world on fire, and the other is probably readily found for a very reasonable price. why would i care if Sigma made one? sorry, don't care. when was that 135mm f2 (or was it 1.8?)IS supposed to drop?

"Q: The 28-70 mm f/2.8 class lenses have been superseded by 24-70 mm f/2.8 instruments. Taking into the account the success of the Sigma 18-35 mm are you already thinking about a full frame construction of that type or rather about e.g. a 28-70 mm f/2.0 or a 28-50 mm f/2.0 model?A: We don’t have a very concrete idea at the moment, yet we will keep on considering designing large aperture zoom lenses."

If I have to choose between the old Canon 24-105 and the new Sigma variation, I will always pick the former regardless of how good the optics are in the latter. One simple reason: AF reliability.

Addendum: From http://www.dpreview.com/lensreviews/sigma-18-35-1-8/5"We shot with a range of Canon SLRs, from the entry-level EOS 100D to the top-of-the-line EOS 7D, and all had problems focusing absolutely correctly all the time. This was usually only obvious when shooting at apertures larger than F2.8. In general, we got slightly better results by using the central AF point (with recomposition) compared to using off-centre AF points, but this didn't eliminate focus errors entirely...

We looked at whether the focus problems we saw from the 18-35mm could be mitigated by using autofocus microadjustments. With a Sigma USB Dock to hand, we set about determining and programming in a full set of autofocus microadjust parameters for all of Sigma's specified focal lengths and focus distances (18, 24, 28 and 35mm; infinity, 0.5m, 0.35m and 0.28m). This took several hours to set up, even with specialised focusing targets to hand...

This procedure certainly improved overall focus accuracy when shooting at the distances used for microadjustment. However these are fixed by the software, and there's no option to specifically correct any distance between infinity and 0.5m. Unfortunately though, the vast majority of subjects end up somewhere in between, and we found that the lens still had some problems with focus accuracy even when fully programmed as above."

I have the Sigma 30 f/1.4 DC HSM Art lens. Its AF accuracy leaves much to be desired even though it is optically sound.

This only reinforces my old belief: avoid 3rd party lenses at all costs.

Actually just thinking on this further; of course Sigma lenses can be made to fit any of the major cameras. Maybe they hope to make the 24-105 as ubiquitous with the other major brands as it is with Canon.

Good point - Nikon's 24-120/4 VR isn't that impressive, might be a market for that mount.

Neither is Canon's. The 24-105 is easily the worst L lens I have ever tried (tried three, couldn't stand to own any of them for even as long as a week).

Sure the 24-70 II is amazing, I have one, but it costs $2000+. LOTs of room under that. The 24-70 f/4 IS also has to beaten and that has been sold for as low as $1025 so that is more of a challenge, but maybe they can manage to beat it for $750 or tie? Also have to beat the Tamron at $1200, although some might not like the bulk of the Tamron.

It is a decent lens, but not really an "excellent" one. It could use way more sharpness across the frame, especially in the corners. I wouldn't use the 24-105L for landscapes.

I shoot landscapes with it very often when I travel. I have comparison shots between it and the 35L. Hard to tell a difference, even in the corners. It is f/11 - f/16 after all. The biggest problem in the corners is not softness but that the objects there tend to be too close.

The resolution potential of all these lenses merge from about f11 onwards. With careful judging of the hyperfocal distance I find f8 is more than adequate on a 35mm, even 5.6 on a 24mm. Makes a huge difference for critical sharpness. The 35L is out of the 24-105's league when used in this way.

Even at f/11 the FF corners and deepest edges on the 24-105 can still be weak in real world complex scenes all too often. The 24-70 II is every bit as good as the 24 1.4 II there OTOH.It is not even sharpness at the corners either, even in the center it doesn't have the same micro-contrast pop as the 24-70 II or 24 1.4 II or 24 TSE II or Zeiss 21 (or likely 24 2.8 IS), but forget sharpness what about stuff like longitudinal CA? 24-105 gets a fair amount of PF/GF. The 24-70 f/4 IS has a good deal less and the 24-70 II has radically less, the 24-70 II is basically almost a true APO (and it also has ultra-precsion AF breaking measurements which mean that it can focus more precisely than most other lenses on a 5D3/1DX).

"Sometimes changes like this that occur during the life of a lens (or camera) are done to address a problem. I can think of a half-dozen examples off of the top of my head; a few announced by the manufacturer but most not announced.

These aren’t always ‘secret upgrades’ as the paranoid among us like to think, but sometimes they are. Most often, though, they’re simply a change in subassembly supplier or a more effective way to manufacture a part, like this one."